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The thermal oxidation rates of Al0.83In0.17N layers grown lattice-matched to GaN and the oxide's optical constants are studied. The ∼230 nm thick AlInN layers are placed into a horizontal furnace at elevated temperatures and exposed to either O2 (dry) or H2O vapor with an N2 carrier gas (wet). The samples are oxidized at different temperatures (830–870 °C) and at a constant time or at various times at a constant temperature of 830 °C. Spectroscopic ellipsometry is used to determine the oxide thicknesses, refractive index, and extinction coefficients. The oxidation rate for the wet conditions is faster than for the dry conditions, and both increase with temperature, as expected. However, the oxidation rate is also dynamic with time and can be fitted with the Deal–Grove model, suggesting reaction rate and diffusion-limited processes like other more mature semiconductors. Finally, the dry conditions produce oxides that expand more than the oxides produced under wet conditions. The ability to thermally oxidize Al0.83In0.17N layers lattice-matched to GaN is a promising process technique for producing new III-nitride-based electronic devices. [ABSTRACT FROM AUTHOR]

The recombination rates in InGaN/AlGaN/GaN multiple quantum wells (MQWs) emitting in the green-yellow and grown with different Al compositions in the AlGaN interlayer (IL) are shown. By transforming measurements on radiative efficiency, absorption, and differential carrier lifetime, the radiative and nonradiative rates are determined. The IL Al composition controls lattice relaxation of the MQWs, as determined by X-ray reciprocal space mapping, and, therefore, defect formation. For the most pseudomorphic MQWs, the Shockley-Read-Hall (SRH) A coefficient is minimized and is similar to reports at shorter (blue and green) wavelengths. It is an order of magnitude smaller than a conventional InGaN/GaN MQW and is the most significant factor behind the improvement in radiative efficiency using the IL. The radiative B coefficient is also reduced and a minimum for the most pseudomorphic MQWs due to a reduction in the electron-hole wavefunction overlap. However, the decrease in A is more significant and leads to an overall improvement in the radiative efficiency. These recombination rate measurements confirm that if the SRH recombination is controlled, then the severe reduction of radiative recombination with an increased emitting wavelength is one of the main challenges in realizing high efficiency, long-wavelength InGaN-based MQW emitters operating at low to moderate current densities. [ABSTRACT FROM AUTHOR]

An active region design based on InGaN / delta-InN quantum well (QW) with AlGaN interlayer (IL) and GaN barriers (delta-structure) is investigated for potential high-efficiency visible light emitters. Numerical simulations demonstrate a large wavelength redshift with a simultaneous increase of the electron-hole wavefunction overlap for the delta-structure as compared to the conventional InGaN QW with AlGaN IL and GaN barriers. Proof of concept experimental growths via the metalorganic chemical vapor deposition demonstrate the effect of the delta-InN insertion into the conventional InGaN-based QW. [ABSTRACT FROM AUTHOR]

The recombination rates in an In0.25Ga0.75N/Al0.48Ga0.52N/GaN multiple quantum well (MQW) structure are measured to identify the cause of low efficiencies in high In-content InGaN quantum wells. The MQWs emit from 640 to 565 nm and are grown using metal-organic chemical vapor deposition (MOCVD). The addition of AlGaN interlayers within the MQW provides strain balancing and suppresses defect formation in high In-content InGaN quantum wells. The rates are found by transforming the optically measured radiative efficiency, differential carrier lifetimes, and optical absorption. Both components of non-radiative recombination rates, Shockley-Read-Hall (SRH) and Auger recombination, are found to be similar to the values of blue-emitting InGaN MQWs. The low SRH recombination rate is attributed to the use of the AlGaN interlayer. The radiative recombination rate, however, is more than an order of magnitude lower compared to blue emitting (lower In-content) InGaN-based MQWs. While this large reduction in radiative rate can be attributed to differences in carrier overlap and transition energy, it may also include effects of variations in thickness and compositional inhomogeneities. [ABSTRACT FROM AUTHOR]

Current-voltage (IV) characteristics of two AlGaN-based deep ultraviolet (DUV) light-emitting diodes (LEDs) with differing densities of open-core threading dislocations (nanopipes) are analyzed. A three-diode circuit is simulated to emulate the forward-bias IV characteristics of the DUV-LEDs, but is only able to accurately model the lower leakage current, lower nanopipe density DUV-LED. It was found that current leakage through the nanopipes in these structures is rectifying, despite nanopipes being previously established as inherently n-type. Using defect-sensitive etching, the nanopipes are revealed to terminate within the p-type GaN capping layer of the DUV-LEDs. The circuit model is modified to account for another p-n junction between the n-type nanopipes and the p-type GaN, and an excellent fit to the forward-bias IV characteristics of the leaky DUVLED is achieved. [ABSTRACT FROM AUTHOR]